Physician, publicist, and historian, b. at Mallow, Cork, 29 February, 1797; d, at New York, 29 May, 1880. His eldest brother Theodore held a commission in the English army; the others, Eugene and David, became priests and were distinguished for their learning. On completing his education in Ireland, Edmund went to Paris (1820) to study medicine. In 1830 he settled in Montreal and besides the practice of medicine, took an active part in the National Patriotic movement and in 1834 became the editor of its organ the "Vindicator". Elected to the Provincial Parliament in 1836 he held a conspicuous position in debate for popular rights, took a leading part in the unsuccessful insurrection of 1837, was attainted of treason, fled to the United States, remained nearly a year the guest of Chancellor Walworth in Saratoga, and in 1838 resumed the practice of medicine in Albany, where he edited the "Northern Light", an industrial journal.

The anti-rent agitation of the time led him to study the land-rights of the Patroons. Attracted by the rich but neglected old Dutch records in the possession of the State, he mastered the Dutch language and in 1846 published the first volume of "History of New Netherland", the first real history of New York State. The result of its publication was the official commission of J.R. Brodhead by the New York State Legislature to search the archives of London, Paris, and The Hague, and to make copies of documents bearing on New York colonial history. These documents were published in eleven quarto volumes (1855-61) under the editorship of O'Callaghan and are a monument of care and ability. In 1848 he was made keeper of the historical MSS. Of New York State, and in this capacity served for twenty-two years. He was the first to call public attention to the value of the Jesuit Relations, and read a paper before the New York Historical Society, giving description of their purpose and scope. James Lenox began to collect the scattered copies and the Lenox Library in New York, contains the only complete set or series of printed Jesuit Relations. The Thwaites edition in seventy-three volumes was based on the Lenox set of the French, Latin and Italian texts. O'Callaghan dedicated to Lenox his "List of the editions of the Holy Scripture and parts thereof Printed in America Previous to 1860". An edition of this work with annotations by Lenox is in the Lenox Library, New York.

In 1870 O'Callaghan went to New York and assumed the task of editing its municipal records, but through difficulties about financial resources they were never published. Though highly esteemed for his medical learning, O'Callaghan's great claim on the gratitude of posterity is his historical work. The clearness of his style with accuracy of detail gave authority to his writings, which contain a mine of original information about New York colonial history.

Published works: "History of New Netherland"(New York, 1846-9); "Jesuit Relations" (New York, 1847); "Documentary History of New York" (Albany, 1849-51); "Documents relating to the Colonial History of New York" Albany, 1855-61); "Remonstrance of New Netherland from original Dutch MSS." Albany, 1856); "Commissary Wilson's Orderly Book" (Albany, 1857); "Catalogue of Historical papers and parchments in New York State Library" (Albany, 1849); "Orderly Book of Lieut. Gen. John Burgoyne" (Albany, 1860); "Wolley's two years' Journal in New York" (New York, 1860); "Names of persons for whom marriage licenses were issued previous to 1784" (Albany, 1860); "Journal of the Legislation Council of the State of New York, 1691-1775" (Albany, 1860); the companion work: "Minutes of the Execution Council of the State of New York", begun by the state historian Mr. Paltsits in 1910; "Origin of the Legislation Assemblies of the State of New York" (Albany, 1861); "A list of Editions of Holy Scripture and the parts thereof printed in America previous to 1860" (Albany, 1861); "A Brief and True Narrative of hostile conduct of the barbarous natives towards the Dutch nation", tr. From original Dutch MSS. (Albany, 1863); "Calendar of the Land Papers" (Albany, 1864); "The Register of New Netherland 1626-74" (Albany, 1865); "Calendar of Dutch, English and Revolutionary MSS. in the office of the Secretary of State" Albany, 1865-68); "New York Colonial Tracts", 4 vols.: (1) "Journal of Sloop Mary"; (2) "Geo. Clarke's voyage to America"; (3) "Voyages of Slavers"; (4) "Isaac Bobin's Letters 1718-30" (Albany, 1866-72); "Laws and Ordinances of New Netherland 1638-74" (Albany, 1868); Index to Vols. 1, 2, 3 of transl. Of Dutch MSS. (Albany, 1870); "Copie de Trois Lettres écrites en années par le Rev. P.C. Lallemant" (Albany, 1870); "Relation de ce qui s'est passé en la Nouvelle France en l'année 1626" (Albany, 1870); "Lettre du Rev. P. Lallemant 22 Nov., 1629" (Albany, 1870); "Lettre du Père Charles Lallemant 1627" (Albany, 1870); "De Regione et moribus Canadensium, auctore Josepho Juvencio" (Albany, 1871); "Canadicæ Missionis Relatio 1611-13" (Albany, 1871); "Missio Canadensis, epistola exPortu-regali in Acadia a R.P. Petro Biardo" (Albany, 1870); "Relatio Rerum Gestacum in Novo_Francica missione annis 1613-4" (Albany, 1871); "Records of New Amsterdam 1653-74", tr. By O'Callaghan were published by Berthold Fernon (New York, 1897).

O'Callaghan, A Collection of MSS. And Letters in the Library of Congress, Washington, D.C., 2 vols. Of documents and 9 vols. Of correspondence; Shea in Magazine of American History, V, 77; Walsh, in Records of Amer. Cathol. Hist. Soc. (March, 1905); Bibl. Bull., no. 26 (Albany, 1901); Report of Brodhead as agent to procure and transcribe documents in Europe relative to Colonial History of New York; New York State Senate Doc., no. 47.

John T. Driscoll.